As I signed in for work at the back door of the Savoy one night, the security man looked at me quizzically: "Where you from, Fran?"

"Manchester."

"What, Manchester in England?"

"Yes, that's right." His puzzled expression gave way to a look of sheer astonishment: "But we never have English people working here!"

The outsourced company that sent me to the Savoy as a cleaner during an undercover investigation for the Guardian didn't have many like me, for sure. I was constantly conscious of being better fed and less tired than my workmates, who juggled three or four jobs and sometimes pinched food to take home. And unlike some of them, I tended to kick off when the wage slip didn't add up or compulsory overtime wasn't paid. Which is why I was both surprised and pleased to see outsourced cleaners at the John Lewis store on Oxford Street threatening to strike this week. Could it be a sign of things starting to change?

Sadly, a closer examination of the facts suggests not. The John Lewis cleaners, who work for a subcontractor called Integrated Cleaning Management, had been drawing the minimum wage of £6.08 an hour for some time – considerably less than the £8.30 the London assembly says they need. Although they are now demanding a living wage, it wasn't the low pay that pushed them over the edge. It was the threat of redundancies and swingeing cuts in hours.

You see, the average agency cleaner doesn't do protest. She – and it mostly is a she – may well have just arrived in Britain, and she may not speak much English. Maybe her immigration status is a bit uncertain. She isn't well connected, and even if she was, she probably wouldn't make a fuss because there'd be plenty waiting to take her place.

Cleaners operate at the sharp end of 21st-century capitalism. They're a casualised, ever-changing army which despite its huge size – about 400,000 at the last count – finds it almost impossible to mobilise. Cleaners rarely congregate in groups of more than a few dozen – there are just 28 in the John Lewis group – and even when they do, they don't all speak the same language – among my workmates at the Savoy were migrants from Zimbabwe, Uganda, Malaysia, Bangladesh and Venezuela, to name but a few.

They are everywhere, yet the white collar workers with whom they share a workplace hardly know they exist. Cleaners arrive in the dark and they often leave in the dark, dragging their aching backsides on to the last bus of the night or the first of the early morning while office workers sleep.

Those in organisations like John Lewis, or like the HSBC bank cleaners who recently won the right to a living wage after a long campaign, are the lucky ones. For it isn't just the big corporates who are outsourcing their dirtiest jobs: we're all at it. One of the biggest growth areas for employment is domestic labour. Britain has acquired an extra 170,000 cleaners in the last 50 years, most doing the odd hour or half-day in someone's home, for cash. How are they ever going to meet up and join a union?

There are some great organisations – Citizens UK, for instance – working to persuade employers to pay a living wage. But we need regulation and enforcement, not persuasion. When the Low Pay Commission complained in 2010 that hotel cleaners were routinely being ripped off, the Revenue promised to act. Two years later they reported that they'd written to 80 hotels and secured back pay for 300 workers totalling a paltry £110 a head. It just isn't enough.

The John Lewis protest is a beacon of hope for others in the same position or worse. But it's a drop in the ocean. It's more than a decade since I worked as a night cleaner at the Savoy, yet little has changed. And unless we have a government that's prepared to push for a living wage and get tough with employers who rip off the vulnerable, I can't see things improving in the next 10 years, either.